A large-sized conveyance vehicle called a dump truck is generally provided with a loading platform called a vessel capable of being tilted in upward and downward directions by using a rear side as a fulcrum on a frame of a vehicle body. The conveyance vehicle is to transport and convey a load to be transported to a transportation destination (an unloading site, a load collecting site) in a state in which the load (crushed stones, earth and sand, for example) is loaded on this loading platform in a large quantity (Patent Document 1).
The conveyance vehicle according to this type of conventional art is composed of an automotive vehicle body, a loading platform provided on a vehicle body for loading a load, capable of tilting (rise and fall) by using the rear side as a fulcrum, and a hoist cylinder provided between the loading platform and the vehicle body and tilting the loading platform upward or downward by extending or contracting when the load is to be discharged from the loading platform.
Such a conveyance vehicle runs to the transportation destination in the state loaded with a load in the loading platform and then, rotationally moves the loading platform upward by extending the hoist cylinder and discharges the load to the unloading site along a tilting direction of the loading platform by this raising operation. On the other hand, after the discharging operation is finished, the hoist cylinder is driven in a contracting direction or the hoist cylinder is contracted by its own weight on the loading platform side, for example. Therefore, the loading platform falls so as to gradually lower to a position where the loading platform is seated on the vehicle body.
Incidentally, running in the state in which the loading platform is not seated on the vehicle body is not preferable since it is concerned that the loading platform might touch an obstacle such as an electric wire, a piping and the like, for example. Patent Document 2 discloses a vessel raised running preventing device configured such that if a tilting angle of the loading platform is at a predetermined angle or more, an accelerator pedal is locked by an actuator, and if the tilting angle of the loading platform is at the predetermined angle or more, normal running is prohibited.